NATURAL SCIENCES OF PHILADELPHIA. 
143 
In regard to tlie geographical distribution of the formation, very little can 
be said. Mr. Englemann, geologist to Lieut. Bryan's Expedition to the South 
Pass, often mentions a similar rock occurring at various localities between Fort 
Laramie and the South Pass.* Dr. Shumard, after an examination of some 
specimens placed in his hands by Mr. E., says : " The specimens from the meta- 
morphosed silicious strata, on the north side of Medicine Bow Butte, are 
Paleozoic types, belonging to the genera Spirifer, Chonetrs, Orthis, Orthoceras, 
Conocardium, &c. They were very badly preserved, and their specific charac- 
ters almost wholly obliterated. From their general appearance, however, I am 
strongly of the opinion that they represent the Devonian period, ' ' The evidence 
of its existence in the vicinity of Fort Laramie and other localities is so slight, 
that I have thought it not prudent to color any portion of the map as Devonian. 
IV. Carboniferous System. 
This system, as it is developed in the region of Fort Laramie, has been dis- 
cussed so fully by Mr. Meek, and the writer in our paper published in March 
last, that I need only refer to it in a very brief manner. The town of Desoto 
is the highest point known on the Missouri where these limestones are exposed. 
Ascending the valley of the Platte river, we find them quite well developed as 
far as the mouth of the Elkhorn, when they pass beneath the bed of the river, 
and the sandstone No. 1 occupies the country. Several small seams of coal 
have been found in these limestones at Belle vue and other localities ; and in the 
valley of the Platte, about ten miles above its mouth, I noticed a bed of very 
dark carbonaceous shale two feet in thickness, cropping out near the water's 
edge. This was considered by the inhabitants as a sufficient proof of the exist- 
ence of a workable bed of coal in the vicinity. The evidence now points to 
the conclusion, that, though these limestones belong to the true coal measures, 
they hold a position above the workable beds of coal, and that it is not proba- 
ble a valuable seam of coal will be found north of the southern line of Nebraska. 
A bed of coal, of inferior quality, has been wrought near Leavenworth City, 
Kansas Territory, but it holds a lower geological position than the limestones 
of the southern portion of Nebraska, the dip of the strata being toward the 
northwest. 
The exact position in the Carboniferous system, to which the limestones 
around Fort Laramie and in the Black Hills belong, is not sufficiently clear from 
the evidence yet obtained. They do not seem to be the equivalents of the beds 
above described along the Missouri, though they may be. The texture of the 
rock is quite unlike that of any of the limestones of the coal measures with 
which we are acquainted, and there seems to be an absence of the fossils char- 
acteristic of the coal measure limestones on the Missouri, and in northeastern 
Kansas. The latest opinion, however, of my associate, Mr. Meek, is, that they 
belong to the true coal measures. 
The following sections may serve to show the relations of the limestones at 
Port Laramie with those in the Black Hills. 
d. — Vertical section of carboniferous rocks near Fort Laramie. 
Yellow magnesian limestone, hard and rather granular in its structure ; 
contains several species Rhynconella, 50 feet. 
c. — ^Very compact bluish gray limestone, with a deeply sinuate Productus, and 
a Productus like P. cora in the fineness of its strise, . . 20 feet. 
h. — Rather friable, flesh colored, arenaceous limestone, with an abundance of a 
smooth Terebratula, like T. subtileta, 4 feet. 
<^ ■ — Yellowish and whitish arenaceous limestone, containing Spirifer, Rocky mon- 
tani, (Marcou) allied to Lower Carboniferous forms ; a second species very 
much like, perhaps identical with, S, cameratus ; a third, with a high 
aj-ea like S. cuspidatus ; also a species of Productus very closely allied to 
P. semirettculatus, 30 to 40 feet. 
* President's Message and Documents, 1857, page 417. 
1858.] 
